1. Field of the Invention
The present invention is related to an apparatus and a method for examining appearances of information recording media. Information recording media typically are disks such as optical disks.
2. Background
In optical disks such as CDs (compact Disks) and DVDs (Digital Versatile Disks), small-sized concaves called “pits” are formed in surfaces of these optical disks, and these pits own information. These pits are optically read by optical pick-up heads, so that sound and pictures may be reproduced. Since optical disks are manufactured by employing a mother disk of these optical disks, structural objects which correspond to the pits are also present on this optical-disk mother disk.
When optical-disk mother disks and optical disks manufactured after injection molding are examined, examining apparatus irradiates the optical disks with light such as laser light, actually read signals of reflection light, and measure completion characteristics of recording operations, signal strengths, noise, and the like based upon the actually read signals in order to examine as to whether or not an error pit is present on the examined optical disks. Conventional examining apparatus are disclosed in, for example, Japanese Laid-open Patent Application No. Hei-9-54952 (refer to pages 3 and 4, FIG. 1), and Japanese Laid-open Patent Application No. 2004-55119 (refer to page 5, FIG. 1).
The conventional information recording medium examining apparatus merely read out optical signals from optical-disk mother disks and optical disks. Therefore, these conventional examining apparatus cannot examine that error pits have what shapes. However, since there is a close relationship between shapes of pits and recording operations, it is desired to provide technical ideas capable of further examining shapes of pits of optical disks.
Also, while disks having large storage capacities are developed, for example, as to an optical disk having a storage capacity of 100 GB (gigabytes), dimensions of concaves/convexs of pits are reached to several 10 nm. Dimensions of these pits are required to be manufactured in precision of 1 nm levels. Therefore, when shapes of optical-disk mother disks and shapes of manufactured optical disks are tried to be examined, examination capabilities in 1 nm precision levels are necessarily required.